Annoying stepper's sound

Thanks TommyL. I opened the box this morning
I can see per board (4 total)
1x PIC16F84A
1x 7805 In TO220 format
4 x IRFZ44N mounted over aluminium bar
1 Crystal 4000 Hz
1x transistor TO 92 format.
4 x power rectifier diodes and electrolitic 4700uF x 25Vcc
4 diodes more (like 1N4007)
Electrolitics, cap. ceramics, resistors, terminals, 1 fuse, etc

Common to 4 boards.
1 Transformer 17 Vca x 3 / 5 A or more
1 Transformer 9 vca 300 mA

So, I need a schematics circuit. If you have one to share with me, please let me know.
I have some photos if you want.

My goal is to reduce the noise as possible...just that.
Regards.

I do not have the schematics, so pictures would be nice, although not very helpful.
You do need that for any modification to it. Interesting to see a PIC , as the better drives use DSP processors for managing micro stepping. Anyway, it looks like the only option for now is just adding 0.1 to 0.47 uf capacitors to power rails if they already do not have them.

Hi TommyL. I've read a little more about the step motor noise.
You' re right. I need to use rubber to maximum noise isolation between the motor and the table frame.
In addition I need to use plastics screws, nuts, etc to secure the motor to the metal table frame.
This appear to be an integral solution to my problem and I'll continue along this line in a first time.
Really y didn't know about the PWM and you colaborate to increase my knowlege.
Thanks a lot.
Best Regards.